Intelligence communication system



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INTELLIGENCE COMMUNICATION SYSTEM 5, 194'? 8 Sheets-Sheet 7 Jan. 2, 1951Filed Dec.

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INTELLIGENCE COMMUNICATION SYSTEM Filed Deo. 5, 1947 8 Sheets-Sheet 8 FAM mkv@ AI Y lx .kw all M All. I

Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE INTELLIGENCECOMMUNICATION SYSTEM Application December 5, 1947, Serial No. 789,978

Claims.

This invention relates to intelligence communication systems. Moreparticularly, the invention relates to such a system wherein selectedintelligence eiects are transmitted and received or recorded by virtueof pulse modulation on a single carrier frequency or on a singlechannel.

Various arrangements have been proposed, or are in use, for reproducing,at a receiver, inteiligence data selected at a transmitter. For example,in a so-called teletypewriter system, a printing mechanism at a receiveris made to respond selectively to operation of a typewriter keyboard ata transmitter.

Such prior art systems have generally been very cumbersome andexpensive, as Well as indirect, sensitive to derangement, and difcult tomaintain. Additionally, such systems usually require several carrierfrequencies or channels for proper operation. The expense ofinstallation and maintenance has been augmented by the necessity ofusing special synchronizing equipment to maintain the receiver in stepwith the transmitter.

One example of such prior art systems uses a voltage variation methodfor transmitting intelligence. This particular system not only requiresseven carrier frequencies or channels but also is unduly complicated,delicate in its adjustments, cumbersome and expensive. In another knownsystem, messages are translated by punching symbols on a tape andtransmitting these symbols. At the receiving end, the speed oftransmitting and receiving these symbols must be reduced, after whichthe symbols are used to actuate a special typing machine. This lattersystem is likewise excessively cumbersome and expensive cue to thenecessity of first translating the message into tape symbols and thenretranslating these symbols into selected characters. This method is, tosay the least, not direct.

In contradistinction, with the system oi the present invention,selection of a given effect at the transmitter directly causes a uniqueseries of pulses, of a predetermined character, to be sent out over asingle channel or carrier frequency. Receipt of this unique series ofpulses v selecting keys arranged in rows and columns as a grid, as on atypewriter keyboard. When a selected key is operated, a series ofpulses, of a predetermined character, are sent out and are indicative ofthe coordinates, such as the row and column position, of the selectedkey.

The receiver includes a printing mechanism having printing devices alsoarranged in rows and columns corresponding to the keys at thetransmitter. The received series of pulses efiects a unique selection ofa printing device in a row and columnthat is, havingcoordinatescorresponding to those of the selected key at thetransmitter.

More particularly, operation of a transmitter key will cause a rstdetermining pulse group, of predetermined character pulses, to be sentout, and varying in number in accordance with one coordinate, such asthe row in which the key is located. The transmitter then operatesautomatically to send out a first conditioning pulse group comprising apredetermined and constant number of pulses, of a different character.This group of pulses conditions the transmitter to next send out anotherdetermining pulse group comprising pulses of the iirst predeterminedcharacter, varying in number in accordance with the other coordinate,such as the column position of the selected key. Following this secondselection or determining pulse group, the transmitter sends out a secondconditioning pulse group of a predetermined and constant number ofpulses of such aforementioned different character. This last pulse grouprestores the transmitter to its equilibrium state, ready to transmit thecode corresponding to the next selected transmitter key.

Reception of the rst, or row selection, group of determining pulses bythe receiver conditions all the printing devices in the selected row foroperation, as, for example, by unlocking the selected row of printingdevices. The following group of conditioning pulses, which are ofdifferent character and always equal in number, switches the pulse pathsin the receiver to condition the column selection arrangement foroperation. When the column selection group of determining pulses isreceived, all of the printing devices in the selected column arepotentially activated. However, as only one printing device in theselected column has been unlocked (by the row selecting pulses), onlyone printing device, corresponding uniquely to the selected transmitterkey, will actually be operated. The last conditioning group of pulsesrestores the receiver to equilibrium to receive the row selectinginformation corresponding to the next key operated at the transmitter.

In a practical embodiment of the invention, the code corresponding to aparticular transmitter key comprises a first group of positive pulses,corresponding to one coordinate, such as the row in which the key islocated, and a second group or positive pulses corresponding to theother coordinate, such as the column in which the key is located. Eachgroup or positive pulses is followed by a single negative conditioningpulse, the rst of which has the function of switching the transmitterand receiver for transmission and reception of column selectioninformation and the second of which restores the transmitter andreceiver to equilibrium.

By Way of a specic example, suppose the key in the second row and thirdcolumn is operated.v

Normally, the transmitter is in such state that, when conditioned forcommunication of intelligence, its circuit paths are arranged totransmit the row intelligence first. By virtue of this fact, when key2-3 is operated, two positive pulses are sent out over the line. Thetransmitter then automatically sends out a negative pulse over the line,and this pulse also switches the transmitter circuits to pick-up thecolumn information. Accordingly, the transmitter now sends out threepositive pulses, corresponding to the third column, followed by a singlenegative pulse, which also restores the transmitter to equilibrium.

When the receiver is conditioned to receive intelligence, its selectivepulse paths are in communication with its row selection mechanism. Thetwo posit-ive pulses therefore select, or unlock, all the printingVdevices in row two. The following negative pulse switches the receiverpaths to its column selection mechanism, so that the next three positivepulses potentially activate all the printing devices in column three andactually operate only the printing device which is also located in rowtwo. Consequently, a unique selection of printing device 2-3 is made.The last negative pulse restores the receiver to its equilibriumcondition.

In a preferred arrangement, depression of a particular key causes a pairof condensers to he connected in circuit, one corresponding to theselected row and the other to the selected column. Each condenser has avalue corresponding to its respective row or column. Thus, the condenserfor row 2 would require two positive pulses to charge it to a,predetermined potential and, when so charged, effects automaticoperation of the transmitter to discharge the condenser which, in turn,effects the transmission of the rst negative pulse. Other pulse numberselection devices may be used, however, such as electronic deviceshaving a predetermined electronic width corresponding to a preselectednumber of positive pulses.

It is necessary to maintain the receiver tied to the transmitter toprevent false operation due to static or noise. For this purpose, thetransmitter is provided with gating means for permitting a continuousseries of uniformlly spaced negative synchronizing or locking pulses toappear on the line during non-operating periods. rlhe receiver has meansmaintaining the receiver locked against reception of freak coded pulses,due to static or the like, during reception of the series of negativepulses.

ToV unlock the receiver when a key is depressed, the transmitter firstautomatically sends out an unlock code or series of positive andnegative pulses. This code is so selected that any freak series ofpositive and negative extraneous noise pulses will not unlock thereceiver unless by the remote chance that the series corresponds exactlyin number, character, and sequence with the unlock pulse group. Thechance of such coincidence can be made as unlikely as desired by properselection of the unlock pulse group.

Typically, such unlock code may comprise a series of positive pulsesfollowed by one or more negative pulses. Operation of a transmitter keywill first cause a pulse number selection device (such as a condenser)to be connected in circuit. After transmittal of the preselected numberof positive pulses, the following negative pulse conditions thetransmitter to transmit the row and column information, as previouslydescribed.

Reception of the unlock code by the receiver actuates a countingmechanism which conditions the receiver to receive the row information,

It is accordingly among the objects of this invention to provide acommunications system in which any selected one of a series of eifectsis selectively transmitted and received over a single channel or singlecarrier frequency.

Another object is to provide such a system in which selection of anyonel of such series of' effects at a transmitter directly causesselective information to be transmitted and received to directlyactivate an indicator at the receiver uniquely corresponding to theselected effect.

A further object is to provide a simplified synchronizing, locking andunlocking arrangement for the transmitter and receiver of such acommunication system, and providing static-free and noise-freecommunication.

A further object is to provide such a system including receiver gatingmeans normally locked during non-operating periods and unlocked only inresponse to reception of a preselected series of differingcharacteristic eifects constituting an unlocking signal.

A still further object is to provide a transmitter effective to transmitseries of characteristic pulses corresponding to the spatial position ofan effect selecting key and a receiver having gating means responsive tosuch series of pulses to select an indicator corresponding uniquely inspatial position to such key.

Still another object is to provide a transmitter effective, uponoperation of a selected effect producing key, to 'transmit a firstseries of characteristic pulses corresponding tov one coordinate of suchkey and a second series of such characteristie pulses corresponding tothe other coordinate of such key, with a pulse or pulse group of adifferent characteristic being transmitted in between such two series ofcharacteristic pulses; and a receiver, operative upon reception or" therst group of characteristic pulses; to select a number of indicatorshaving the same one coordinate as such key, upon reception of theintermediate pulse or pulse group of different character to switchgating devices to a selection arrangement for the other coordinates,and, upon reception of the second series of characteristic pulses, toselect uniquely the one of such number of indicators having the sameother coordinate as the selected key.

Another object is to provide such a communications system which issimple, silent, compact, portable, inexpensive to construct, install,operate and maintain, and rugged in operation.

These, and other objects, and advantages and novel features of theinvention will be apparent from the following description and theaccompanying drawings. In the drawings:

Figs. 1 and 2 are block diagrams, respectively, of a typical signaltransmitter and a typical signal receiver embodying the principles ofthe invention.

Figs. 3 and e are schematic wiring diagrams illustratingtypicalelectronic components of the transmitter of Fig. l and thereceiver of Fig. 2 respectively.

Figs. 5 and 5A, together are a block diagram illustrating thetransmission of a predetermined signal with the transmitter of Fig. 1.

Fig. 6 schematically illustrates the signal as it appears on the line atthe output of the transmitter.

Fig. 7 schematically indicates the reception of the signal shown in Fig.6 by the receiver of Fig. 2.

Fig. 8 is a block diagram, similar to Fig. l, illustrating addedelements for transmitting synchronizing and unlocking signals to thereceiver.

Fig. 9 is a schematic representation of the signals appearing on theline before, during and after the transmission of a predetermined signalcode.

Fig. 10 is a block diagram, similar to Fig. 2, illustrating the receiveras modied to respond to the synchronizing and unlocking signals providedby the transmitter of Fig. 8.

Referring to the drawings, the signal transmitter of the invention isillustrated in block diagram form Fig. 1, and Fig. 3 illustrates typicalelectronic components of the transmitter. As stated, an effect selectingarrangement is provided at the transmitter which, upon depression of akey representing a typical character or eiect to be transmitted,activates the transmitter to transmit a group of pulses of a certaincharacter corresponding uniquely to that particular character. Forexample, if a typewriter keyboard is used as a keying or coding device,a coded series of pulses will be transmitted corresponding to therelative .A

position of the key depressed on the typewriter. Thus, assuming that thekey depressed is in the second row from the bottom of the board and inthe third column from the left of the keyboard, the code transmittedwill be 2-3. That is, the irst group, of two pulses, is representativeof the row in whichthe key is located and the second group, of threepulses, is representative of the column in which the key is located. Aswill be made clear, after the transmitter has sent out two pulses of apredetermined character indicating that a key in the second row has beenactuated, the transmitter is automatically conditioned to send out apulse of an unlike or opposite character to condition the receiver toreceive the next group, of three pulses, indicating that the depressedkey is in the third column. The transmitter is then conditioned to sendout a second pulse of such unlike or opposite character which restoresthe transmitter to its state of equilibrium and restores the receiver toa condition to receive the next coded series of pulses.

In a typical arrangement, the depression of a key in row 2, column 3will cause the transmitter to send out the following sequence of pulses;two positive pulses, one negative pulse, three positive pulses, onenegative pulse. As will be described more fully in connection with Figs.8, 9 and 1U, a synchronizing and unlocking arrangement is provided forstatic-free and noise-free transmission and reception of the signals, sothat the receiver will be maintained in step with the transmitter at alltimes, and will be responsive to code transmission only upon receptionof a predetermined unlocking code. It may be stated at this point that atypical arrangement for synchronizing and unlocking comprises acontinuous series of negative pulses transmitted by the transmitter andreceived by the receiver during non-operating periods. The receiver isthus maintained in step with the transmitter, and an unlocking code isprovided whereby the receiver will not respond to false pulses, such asdue to static or the like, unless in the very remote event that suchpulses may accidentally correspond to the unlocking code. Typically,.such unlocking code, which is transmitted when a key is depressed andprior to the transmission of the key identifying code, may comprise acode consisting of a plurality of positive pulses followed by a singlenegative pulse. This conditions the receiver to operate in response tothe transmitted codes corresponding to the selected characters operatedon the keying device o the transmitter.

Figs. 1 and 3 show the fundainentalsoi the transmitter, but without thesynchronizing and unlocking arrangements in order to simplify theunderstanding of the invention. Referring to Fig. 1, a keying device i!)is provided which, upon depression of a particular key activates a pulseformer I5. A ring counter 2d comprising, in the example shown, threetubes 2|, 22 and 2t are activated by the pulse former. Tube 23 isnormally non-conductive in the equilibrium state of the transmitter,whereas tubes 2| and 22 are heavily conducting in such state. Theselatter tubes control the condition of a pair er gating tubes 3Q and 35so that, in the equilibrium state of the transmitter, these gating tubesare not effective to pass pulses generated by pulse generator 25.

A pulse amplifier and inverter 40 is provided including a section 4|connected to gating tube 30 and a section 42 connected to gating tube35. Section 4| is connected, through a negative pulse suppressor 50, totrigger tube 5|] and a section 8| of an output mixing cathode follower8|). Similarly, section 42 of amplifier-inverter 40 is connected,through a negative pulse suppressor 55, to a trigger tube and section 82of cathode follower 8. The latter is connected to transmit pulsesthrough output amplifiers to the line, which may either be a metallicconductor, such as a wire or the like, or a single radio channel havinga predetermined carrier frequency. Terminals 5| and 55 associated withkeying device l0 are connected, respectively, between each pulsesuppressor and each trigger tube.

The trigger tubes 6D, 65 are connected to a one-shot multi-vibrator 'mcomprising three tubes ll, l2 and 73. In the equilibrium state of thetransmitter, tubes 'll and I2 are non-conducting and tube 'E3 is heavilyconductive. Likewise, terminal 5| is grounded and terminal 56 is open.

In the illustrated example, four keys |-I, I-2, 2|, 2 2, arranged incolumns and rows to form a grid, are shown, but it will` be understoodthat a complete keyboard corresponding to all the desired characters isprovided. Terminal 5I is connected to ground I3 through the uppercontacts of keys 2-I, 2--2, I-Z and I-l. Another path to ground isprovided through condensers I4 and I6. Terminal 56 is connected to thelower contacts of keys I-I and 2-l through va condenserY IFF, andv thelower contacts of keys I-2. andA 2 2. through a condenserV I8.. If keyI-I,. corresponding to.V a. character in column I and.. row I, isdepressed, terminal I is disconnected from ground I3 and terminal 56f isgrounded at I3. through condenser Il.. Condenser Id is. now shortedthrough the upper con:- tactsl of keys 2.-I and, 2..--2 and terminal.5I. is connected through condenser Iii` toV- ground. I9.

Depression of; key I-I thus connects termina1.5I: to ground I9: throughcondenser I6, and terminal to ground I3 through. condenserV Il. Pulseformer I5. is activated. by connection to ground. I3 through key I-I,and feeds one posi.- tive pulse into the ring counter 20. This positivepulse causes tube 23 to become conducting and tube 2l to becomenon-conducting. When tube 2.! becomes non-conducting. its potential israised sufciently to bring gating tubeA to the conducting level and thusopen this gating tube.

A positive pulse from pulse generator 25 is then fed through. gatingtube 3d into section lli of amplifier-inverter ll. In going throughgating tube 3B, the positive pulse is amplified and inverted so that itenters amplifier-inverter I8 as anegative pulse. In the latter, thepulse is again amplied and inverted so that it passes through negativepulse suppressor 5c as a positive pulse.

The size of condenser I6, corresponding to keys in row I, isy soselected that a single pulse is sufcient to charge the condenser to sucha potential as. to bring trigger tube G above its cut-olf value. Thiscauses the One-shot multi- Vibrator 'I' to flip,r while the positivepulse is transmitted to section 8l of cathode follower 8U, amplified andsent out on the line. When the multi-vibrator is tripped or ilips, tube'II conducts and discharges condenser I6 through terminal 5I. Theresulting negative pulse formed when electron tube 'II conducts, is fedthrough the. line through the: cathode followerY 8.0;

When;the:multi-vibrator. iiips, tube I3 goes, to the noni-conducting4state, causing. a positive pulse.` to. be transmittedtoring counter 2B.;This positive pulse causestube 2 I to again becomeconductive. which inturn causes.v tube. 22.to, become non-conductive. The resultinghigh-potential of tube 221; renders gating tuba conductive..v As tube2d; is` again conductive, its potential is so low.` that gating tubexzbecomes non-conductive or. closed.

Undery these. conditions, a. positive pulse; from pulsegenerator 25. isfed to` gating. tube 3.5 Where itis ampliedandinverted and fed'. as: a.negative pulseftoisection. 62 of. amplier-inverter im. The pulseisagain amplified: and inverted and fed as a positivepuisethroughnegative. pulse;v suppresser ;-and1thus. through sectioni ofcathode follower. till and.. the. output amplifier. to. the line. Thesize, of; capacitor, or condenser. Il., corresponding to keys in column.I, is so chosen that this single positive pulse is suicienti to chargethe4 condenser through terminal 5.6,. to such. a potential as will causetrigger tube 65 to. conduct effecting,V a flip ofthe. multi-vibrator:1li. Tube l'r2,now becomes conductive anddischarges condenser IIYthrough terminal 5B causing a negative` pulse'to be applied toA the linethrough cathode follower SIB; As tube l2: becomes con.- ductive, tube'I3 in turn becomes non-conductive and causes a positive pulse to betransmitted to ring counter 20:. This pulsel causes tube 23. to becomenon-conductive, thus restoring the transmitter, to its. state vofequilibrium.

In a manner which will be apparent: upon'zinspection,. depression of.key 2*--2', for example, will connect terminalsa 5.-If and.. 56;' to=ground through. condensers/ t4: and |18: respectively.. As key 2 2 isfinthe. secondv row andthesecond column, the. size of condensers |41 and;I8 isiso selected that it will take two positive pulses to chargeeachof.these condensers to the required potentiaL. thus applying: the; codev2*-2 toe the lihe';. Similarly', if; key Ze-I wereractuatedgterminals 5Iand 55 would be connecte'dto ground through condensers I4;- and I1,respectively. Thus, the. code. 2-IA wouldbesappli'edv to: the' line.When key I-Zli is depressed, the. connectonof terminals ESI' and 56,1t0.ground is.' through condensers It and'l I3? respectively, which .requireone pulse and two pulses, respectively, to chargefthem, thus applying;the. code I-2. to -thelin-e;

In general. then if a keyv ink the: row and the y column is depressed,the information which would appear on the line would comprise fcpositive pulses, followed' by one negative pulse, and then y positive.pulsesY which. are. in turn followed by one negative pulse.

Referring. to Fig. 3, the. electron tubes 2I.`,. 22, 23 forming ringcounter 2S" are: shown asftriodes, although' itr is. possible to make`the ring counter by using diodes, triodes, tetrodes, pentodes or dualpurpose tubes, etc. Tube 25|: has itsplate connected to the: controlgridof: gating' tube 3d, and tube 22 has its platesc'onnectedit-o thecontrolgrid of gating tube. 35. Tubes; 33 and 35;. are: shown as pentodetubes which.. act-as.: gates; or escapement devices. Although pentodes;are shown, diodes, triodes, tetrodes, or pentagrid". tubes. may be usedfor 3&2 and 35; Sincethe' plate potentials of. tubes 2i and. 22 arelow,. as'these tubes. are conducting. under equilibrium. conditions ofthe transmitter, gates-35 and35" are. normally closed.

Amplifier-inverter Azil'is shown as atwo-section tube, although twoseparate triodes, tetrodesA or pentodes may be usediif desired. Pulse.generator 25 is capacitativel'y coupled. through a shielded cable togates 3Q. and 35 which are capacitatively coupled respectively ofsections- III and'. 82 of tube de.

The negative'pulsesuppressors Eiland 551comprise rectifying devices,ldiagrammatically. illustrated, which are so arranged as to prevent. thepassage of negativepulses therethrough, and/the pulse. Suppressors areconnected throughshielded cables to trigger tubes i513` and 65. These.latter tubes are non-conducting because they are. biased below cut-cir.The tubes 'II' andv "I2, which. are shown as pentodes, arethenon-conducting tubes of the one-shot multi-vibrator'Ill-whereaspentode I3 is a conducting tube of the multi-vibrator;

The pulse former I5: includes abatteryfZcoupled through acapacitance 2lyto rectiers'28, 23 and to thering counter Zell'through. an arrangementcomprising rectiers 3 I, 32. Tube '5:3 is connected to ring counter. 2Ethrough aconductor 3:3 capacitatively coupled; to the plate of tube1.3;.

The output amplifying arrangementY comprises a triodecapacitatively:coupledY to the cathode 83 of cathode.follower.r S5.This: latter is shown as a two-section tube, although separate triodesmay be used. A. plate of triodei 9B is capacitative'lycoupled totheinput of a pentode 95 which further amplies-the signals and iscapacitatively coupled to the output terminals 95, 91. These terminalsare connected either metallically or over a radio frequency channel tothe receiver.

It is the function of thev receiver, shown'in block diagram of Fig.2,.to decipher thecode data sent out by the transmitter and causes theproper key or the like in a printing device to be operated in accordancewith a key operated on the transmitter. As shown in Fig. 2schematically, the receiver includes a positive pulse suppressor |55,and a negative pulse suppressor |55. The latter is connected to a rowgate tube HQ in parallel with a column gate tube H5. Row gate tube isconnected through an amplifier |25 to a threering counter |51]comprising tubes |5|, |52, |53. Similarly, column gate tube is connectedthrough an amplifier |25 to a three-ring counter |50 comprising tubesMii, |52 and |53.

Ring counter |55 controls row selection tubes generally indicated at 'IGand shown, for illustration purposes only, as including a pair of tubesand |12 corresponding to row I and row II respectively. Ring counter |50controls column selection tubes indicated at IB!! as including a pair oftubes |8| and |32 corresponding to column I and co-lumn II respectively.The row and column selection tubes control the printing or otherindicating device |55. For illustration purposes, this printing deviceis indicated as solenoid operated printers |52, |2| and |22, arranged inrows and columns to form a grid, and corresponding. in spatial position,respectively to keys |-2, 2| and 2-2 of thev transmitter.

Positive pulse suppressor |55 is connected through an amplier |35 to anip-nop |45 comprising a pair of tubes il!! and |42. Under normalconditions of equilibrium in the receiver, tube 4| is non-conducting andits plate potential controls row gate tube H5. As tube l! isnon-conducting, its potential is high enough so that tube H0 is open orconducting. Similarly, tube |42 is conductive and, as its platepotential controls column gate tube H5, the latter is closed ornonconducting.

In row ring counter |55, tube |5| is normally non-conducting and tubes|52, |53 are normally conducting. These latter tubes control rowselection tubes and |72, respectively, which are thus closed ornon-conducting. Similarly, in column ring counter |55, tube I5! isnormally nonconducting and tubes |52, |53 controlling column selectiontubes IBI, |52, are normally conductive. Thus, the column selectiontubes are normally non-conducting or closed.

For the purpose of describing the operation of the receiver, it will beassumed that element or key of the transmitter has been depressedcausing the following sequential code to be sent out over the line: onepositive pulse, one negative pulse, a second positive pulse, and asecond negative pulse. When this information reaches the input line IDIof the receiver, the iirst positive pulse flows through negative pulsesuppressor |05, open row gate tube Il!) and amplifier |25. Thisactivates row ring counter |50 to count (l). Tube |52 thereupon becomesnon-conductive, making tube |72 conductive selecting the printingdevices ||2 in row I. The first negative pulse following this positivepulse passes through positive pulse suppressor |55 and amplifier |30causing tube |42 to become non-conductive which makes tube |4|conductive. This in turn makes column gate tube ||5 conductive and rowgate tube non-conductive. The succeeding positive pulse thereupon passesthrough negative pulse suppressor |55, column gate tube ||5 andamplifier |25. This causes column ring counter |62I to count (l). Tube|52 becomes non-conducting, rendering column gate tube |8| conducting.This selects devices and `|2| in column I. As co1- umn'l and row I haveboth been selected, the printing device is uniquely determined effectingoperation of this printing device to give an indication identical withthat selected by depressing key of the transmitter. The second negativepulse causes tube 4| to become nonconductive and tube |42 to becomeconductive.

When the printing device or indicator operates, the ring counters |55and |50 are returned to their equilibrium position in which tubes |5|and |6| are non-conducting. This is accomplished for example by vmeansof a microswitch (not Shown) opening the cathode circuits of tubes I 5|,IBI upon operation of any of the printing devices. The receiver is thusrestored to its equilibrium condition and is ready for the next group ofpulses.

Fig. 4 illustrates the electronic components of the receiver. Positivepulse suppressor |09 is illustrated as an arrangement of rectifierseffective to pass negative pulses but not positive pulses and negativepulse suppressor |05 is illustrated as an arrangement of rectiiierseffective to pass positive pulses but not negative pulses.

Suppressor |55 is connected capacitatively to gate tubes Hi) and H5.These latter tubes are capacitatively coupled to two-section ampliers|25 and |25, respectively, which may be dual triodes. The amplifiers areconnected Ycapacitatively, through directional rectifying devices, tothe ring counters |553 and |55. To avoid duplication and simplify thedrawing, amplifier |25 and ring counter |60 have been shown in blockform only, as their electronic arrangements are 'similar with amplifier|20 and ring counter |55 respectively. The tubes of the ring counter I5G are two-section tubes, and tubes |52 and |53 are directly coupled torow gate tubes |72 respectively,r and tubes |62, |63, of ring counter|58, column gate tubes ISI, |82 respectively.

Suppressor |55 is capacitatively coupled to an electron tube amplier|35' which is in turn capacitativelv coupled to a two-section tubeforming the Hip-flop |55. Section of tube |41) controls row gate tube lIU and section |42 controls column gate tube I5.

Fig. 5 shows the actual sequence of operation of the transmitter insending out the code of pulses corresponding to the depression of keyWhen key of the keying device l5 is depressed, a positive pulse goes toring counter 2|) which opens gating tube 3e. A positive pulse from pulsegenerator 25 is amplified and inverted in tube 30 and again amplifiedand inverted in tube Ml. This pulse passes through negative pulsesuppressor 5i) and charges the condenser connected to terminal 5|. Thepositive pulse is then sent out on the line through cathode :followerBil. Also, trigger tube 5i; becomes conducting, causing the one shotmultivibrator 70 to flip which, as described, sends a negative pulse outon the line through cathode follower Bil. A positive pulse is at thesame time applied to ring counter 25 to open gate tube 35.

A second positive pulse then passes from pulse generator 25 through gatetube 35, amplifierinverter 40 and negative pulse suppressor 55 to chargethe condenser connected to terminal 55. This second positive pulse thenappears on the line through cathode follower 8l). Trigger tube 55becomes conductive, causing by means of lil a negative pulse to be sentout on the line through cathode follower 8i) and a positive pulse Ilto.A be applied to ring counter 20 restoring the transmitter toequilibrium. The series. of pulses sent out on the line isdiagrammatically shown in Fig. 6 as comprising a, positive pulse I,negative pulse Il, positive pulse III and negative pulse 'lhisinfomation is received byv the receiver asv shown. in Fig; '7. The iirstpositive pulse I passes through negative pulse suppressor |ii, row gatetube H 9, arnpliiier |20, row ring counter |50.' and row selection tubeto select either of. the printing devices 1| ||2 in row 1. The followingnegative pulse II passes through positive pulse suppressor lil-il,amplier ma to operate flip-flop hln opening column gate tube H5 andclosing row gate tube H0.

The next positive pulse III passes through negative pulse suppressor|55, column gate tube H5, ampliiier |25` and column ring counter |59tooperate column gate tube |8| which completes the selection of printingdevice The second; negative pulse'l IV passes through positive pulsesuppressor |09A and ampli-lier |1301 to operate dip-flop |413 openingrowgate tube Il! and closing column gate tube H5. As described above,operation of the printing device restores the' ring counters |59 and |66toa state of equilibrium'.

the basic system just described. means have been provided to transmitsignaly intelligence data from a transmitter to av receiver. However;the means for checking the. transmitted data for accuracy or forinsuring proper synchronization between the transmitter and receiverhave been shown and described. Figs. 8 and 10 illustrate these controlfeatures as added; toY the transmitter and receiver of Figs; l and 2.respectively. As shown in Fig'. 8'. which is a block diagram. of thecomplete transmitter, a pair of gates Zilliv and' 235 are connected. inperallel with gates 3'1 and 35, to signal generator 25. An. extrasection 2M isY added to the amplier inverter 4.5i, prefereblv comprisinganother electron tube. An additional negative pulse suppressor 25o isconnected in series with amplifier inverter 24|), and' this pulsesuppressor is connected to an additional trigger tube 2ML A condenser20a? .is connected to the line between suppressor 25D and trigger tube2M. A1 fourth. tube 2M' is. added to the one-shot multi-vibrator 1F52and a fourth tube 2211Y is added to the ring counter" 2'0 making theYlatter a ring counter of' four. Additionally, sections 223 and 2M areadded to the cathode follower 8B;

Inl the eouilibrium position, ring counter tube 22' is non-conductiperwhich in turn rend-ers gate 235 conducting. Positive pulses from pulsegenerator 215' then flow through gate tube 2&5 where they'are ampli'edand inverted. as schematically shown. to emerge as'negative pulses.These negative pulses appear op the line through section 284 of vcathode.follower 80.

Thus; before any key in keying device Iii isdepressed. the informationon the line will be a series of negative pulses as'shown in section 25|of the. pulse diagram illustrated in Fig. 9.

If element" is now depressed; theA ring counterZll is stepped to tube22'sl which becomes non-conducting thus opening gate tube 23B. Positivepulses from generator 25T are amplied and inverted in the tube 2343,again ampl'iied and inverted in tube 24|! and pass through' negativepulse suppressor 259' to charge condenseril. If, for example, thesizeof'condenserZil is such that it: takes four pulses to chargefthe;condenser, trigfger tube 260 will become conductive when four` pulseshave been transmitted.. This trips multivibrator lil, dischargingcondenser Zii and causing a negative pulse to appear on the line throughsection 283 of cathode follower Sil'. Also, ring counter 2Q is trippedtoopen gate 39. The code isr then transmitted to the line in the samemanner as previously described in connection with Fig. 2. The lastnegative pulse of the code trips ring counter 29 to again open gate 23.5to permit a stream of negative synchronizing or lookin-g pulses tobesent out on the line through cathode follower 3U'.

Fig. 9 illustrates the sequence of pulses if key is depressed'. Thefirst series of pulses' 215i are the negative synchronization pulses.Whenkey is depressed, the unlocking pulse group 252 or code appearscomprising four positive pulses, for example, followed by a negativepulse. The code comprising two positive pulses. each followed by anegative pulse then appears onthe line as at 253 and is followed bythesynchronizingnegative pulses 25 i. If now key 2--2 is operated, theunlock code- 252V appears on the line followedy bythe-code 2-2 as shownat 25d. After theV code corresponding to key 22 has been sent, negativesynchronizing pulses 25| again appear on the line.

The pulse series is thus divided into' four groups for transmittingdata. The rst group is a seriesA of negative pulses which appearat alltime when no key is depressed, and which have the function ofkeeping thereceiver locked to the. transmitter bypermitting no static or noise toactivate the receiver and also insuring the return of the receiver" toits equilibrium position. The neXtg-rou-pis anunlocking pulsegroup-consisting of' any combination of positiveA and negative pulses ina predetermined code (suchv as four positive, one negative) in thevright order to unlock the receiver so that it may receive informationfrom the transmitter. This groupis followed byI a third group comprisingpulses correspond'- ing to the particular key depressed. TheA iinalgroup thesynchronizing series of negative pulses.

Fig. l0 illustrates the-receiver of Fig. 2 as-modi- 'ed for thesynchronizing and unlocking action. As shown, a counter 39u: comprisingtubes Bill', 302', H33Y is added. Alsof gates siii; 3H, 355' and 35%Aare added as well as an additional tube ill?, to the nip-flop Milfmaking the latter a ring counter of three.

In: the equilibrium' state of the receiver, tube U53v is non-conducting.Gate 3|@ is' open. tubes iii andY H12 are conducting and` gates il@ and||5 are closed. Tube 393- is in its` zero.k position which keeps gate 3|if open andl gate'- si@ closed;

As long as negative pulses appear on the line, the counter Sil@l ismaintained in its zero" position regardless of whether the pulses arestatic or negative pulses are sent out from the transmitter; since thesenegative pulses ilow through positive pulse suppressor Hill.,amplifier-inverter 961i, gatev 3i l, and' intoy gate SiS, thuscontinually causingV gate 3io? to become non-conductinger 300 causinggate 3H to close and gate 315 to open. The single negative pulsefollowing the four positive pulses then ows through suppressor and gate315 to cause counter Hic to count (1). This closes gate 3H) and opensrow gate HEI, permitting the row selecting information to iiow to therow ring counter |50.

The negative pulse following the row information ilows throughsuppressor Miti, amplifier-inverter iti) and gate M5 causing counter Miito again count (l). This closes rovv gate tube Ht and opens column gatetube H5, permitting the column selecting information to flow to columnring counter |60.

The first negative pulse following the column information trips counterI 4l). Tube 442 which has been non-conducting now becomes conductingcausing a negative pulse to appear at gate 3 i 6. This momentarilybreaks the cathode circuits of the tubes of counters Sil restoring thecounter to its equilibrium condition. Such restoration opens gate 3l iand closes gate 3 i 5, and at the same time tube M3 becomesnon-conducting which opens gate 32B. The receiver is now in itsequilibrium condition.

Thus, the system of the present invention involves the transmission andreception of intelligence by the use of coded pulses of a predeterminedcharacter. Fach intelligence identifying' pulse group is delineated andbounded by one or more pulses of a different character. These latterpulses are also utilized to lock the receiver against operation onreception of false signals, such as static` noise or the like.

IThe use of the gating arrangements in the receiver to route successiveintelligence identifying pulse groups to their characteristicallyresponsive recording device, enables the intelligence to be transmittedover a single channel or radio frequency. The positioning pulses, whichdelineate and bound the determining pulse groups, act as the gateselect-ion devices.

The system is peculiarly useful in a teletype- Writer system. in whichthe spatial coordinates of each transmitter key are reproduced at areceiver typewriter. It will be understood that, when the invention isembodied in such system, coded pulses may be used to select upper andlower case characters and also to transmit actuations of the space baror typewriter platen.

While particularly adaptable, as described, to transmission ofintelligence by selecting intersecting recorder coordinates at thereceiver cor responding to intersecting selector coordinates at thetransmitter, the system may be used in coniunction with other uniquequalities of a selector key to uniquely determine a recorder havingcorresponding qualities.

Also, while specific embodiments of the invention have been shown anddescribed in detail, and using specific pulse codes for examples, toillustrate the application of the invention principles, it will beunderstood that the invention may be otherwise embodied Withoutdeparting from such principles.

What is claimed is:

1. An intelligence communication .system com prising, in combination, atransmitter; a receiver; a singe ransmission channel operatively inter-=connecting said transmitter and said receiver; means in saidtransmitter, operable during periods of non-communication ofintelligence, to feed a continuous series of first pulses, of apredetermined character, into said transmission channel; means in saidreceiver, responsive to receipt of said series of first pulses from saidchannel, to lock said receiver in step with said transmitter; means forselecting an eiTect to be transmitted; means for translating theselected effect into a group of second pulses, diering in character fromthe rst pulses and varying in number in accordance with the effectselected, and a group of the first pulses constant in numberirrespective of the effect selected; means in said receiver, responsiveto receipt of such group of second pulses, to reproduce the selectedeffect; and means in said receiver, responsive to receipt of such groupof rst pulses, to restore the receiver to the locked equilibriumcondition.

2. An intelligence communication system comprising, in combination, atransmitter, a receiver; a single transmission channel operativelyinterconnecting said transmitter and said receiver; in said transmitter,operable during periods of non-communication of intelligence to feed acontinuous series of first pulses, of a predetermined character, intosaid transmission channel; means in said receiver, responsive to receiptof said series of rst pulses from said channel, to lock said receiver instep with said transmitter; means for selecting an effect to betransmitted; means responsive to selection of an effect to feed intosaid channel an unlocking pulse group comprising a number of secondpulses, differing in character from the rst pulses, followed by at leastone rst pulse; means responsive to receipt of the unlocking pulse groupto condition the receiver to receive transmitted intelligence; means fortranslating the selected eifect into a group of second pulses varying innumber in accordance with the effect selected, and a group of the firstpulses constant in number irrespective of the effect selected; means insaid receiver, responsive to receipt of such group of second pulses, toreproduce the selected effect; and

-means in said receiver, responsive to receipt of such group of firstpulses, to restore the receiver to the locked equilibrium condition.

3. An intelligence communication system comprising, in combination, atransmitter; a receiver; a single transmission channel operativelyinterconnecting said transmitter and said receiver; means in saidtransmitter, operable during periods of non-communication ofintelligence to feed a continuous series of negative pulses into saidtransmission channel; means in said receiver, responsive to receipt ofsaid series of negative pulses from said channel, to lock said receiverin step with said transmitter; means for selecting an effect to betransmitted; means for translating the selected eiTect into a group ofpositive pulses varying in number in accordance with the eiect selected,and a group of at least one negative pulse constant in numberirrespective of the effect selected; means in said receiver, responsiveto receipt of such group of positive pulses, to reproduce the selectedeffect; and means in said receiver, responsive to receipt of such groupof negative pulses, to restore the receiver to the locked equilibriumcondition.

4. An intelligence communication system comprising, in combination, atransmitter; a receiver; a single transmission channel operativelyinterconnecting said transmitter and said receiver; means in saidtransmitter, operable during periodsl of non-communication ofintelligence to feed a continuous series of negative pulses into saidtransmission channel; means in said receiver, responsive to receipt ofsaid series of negative pulses from. said channel, to lock said receiverin step with said transmitter; means for selecting an effect to betransmitted; means responsive to selection of an effect to feed intosaid channel an unlocking pulse group comprising a number o1 `positivepulses, followed by at least one negative pulse; means responsive toreceipt of the unlocking pulse group to condition the receivedtransmitted intelligence; means for translating the selected eiect intoa group of positive pulses varying in number in accordance with theeiect selected, and a group of at least one negative pulse constant innumber irrespective of the eiect selected; means in said receiver,responsive to receipt of such group of positive pulses, to reproduce theselected eiect; and 4means in said receiver, responsive to receipt ofsuoli group of negative pulses, to restore the receiver to the lockedequilibrium condition.

5. An intelligence communication system comprising, in combination, atransmitter including pulse generating means and a bank of eiectselecting devices arranged in intersecting columns and rovvs to form agrid; a receiver including a bank of eiect reproducing devices arrangedin intersecting columns and rows to form a grid, rovv selecting means,and column selecting means; a single transmission channel extending romsaid transmitter to said receiver; means in said transmitter, operableduring periods of non-communication of intelligence to feed a continuousseries of negative pulses into said transmission channel; means in saidreceiver, responsive to receipt of said series of rst pulses from saidchannel, to lock said receiver in step with said transmitter and blockreceipt of pulses by said row and column selecting means; first means,responsive to actuation of an effect selecting device, to feed into saidchannel an unlock code comprising at least one positive pulse followedby at least one negative pulse; means in said receiver, responsive toreceipt of such unlock code, to direct a succeeding pulse group to saidrow selecting means; second means, responsive to actuation of such eiectselecting device, to feed into said channel a signal code comprising, insequence, a rst determining pulse group, including at least one positivepulse, varying in number in accordance with the row in which theactuated selecting device is located, a first conditioning pulse group,including at least one negative pulse, constant in number irrespectiveof the eiect selected, a second determining pulse group, including atleast one positive pulse, varying in vnumber in accordance with thecolumn in which the actuated selecting device is located, and a secondconditioning pulse group, including at least one negative pulse,constant in number irrespective of the eect selected; said roW selectingmeans, responsive to reception of such rst determining pulse group,selecting the reproducing devices located in the rovi corresponding tothat of the actuated selecting device; means, responsive to reception ofsuch rst conditioning pulse group, to condition the receiver to directthe second determining pulse group to said column selecting means; saidcolumn selecting means; said column selecting means, responsive toreception of such second determining pulse group, selecting thereproducing devices located in the column corresponding to that of theactuated selecting device; whereby, upon actuation of a selectingdevice, a uniquely corresponding reproducing device is selected; means,responsive to reception of the second conditioning pulse group, tocondition the receiver to direct the next received determining pulsegroup into said row selecting means and, responsive to transmission ofthe second conditioning pulse group, to condition the transmitter toagain feed such series of negative pulses into said channel.

BASIL RUYSDAEL. HAROLD L. HADDEN. HERBERT I. ZAGOR. FRANCIS J. ALTERMAN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS- Number Name Date 316,698 Hoevenbergh Apr. 28,1885 1,383,750 Parker July 5, 1921 1,709,031 McCoy Apr. 16, 19292,013,671 Roe Sept. 10, 1935 2,425,307 Desch Aug. 12, 1947 FOREIGNPATENTS Number Country Date 687,419 Germany Jan. 29, 1940

